4 THE AMERICAN MONTHLY [Jan 
ditions favorable for the development of life, without 
however, being able to produce it. Spallanzani’s critics, 
however, objected to his experiment on the ground that 
air is essential to life, and that in his flasks the air was ex- 
cluded by the hermetieally-sealed necks. Schulze (1836) 
set the objection aside by filling a flask only half full of 
distilled water, to which animal and vegetable matters 
were added, boiling the contents to destroy the vitality 
of any organisms which might already exist in them,then 
sucking daily into the flask acertain amount of air which 
had passed through a series of bulbs containing concen- 
trated sulphuric acid, in which it was supposed that what- 
ever germs of life the air might contain would be destroy- 
ed. This flask was kept from May to August; air was 
passed through it daily, yet without the development of 
any infusorial life. It must have been a remarkably germ- 
free atmosphere in which Schultze worked, for, as was 
shown by those who repeated his experiment, under the 
conditions that he regarded as certainly excluding all life, ° 
germs can readily enter with the air. The term “infu- 
sorial life” having been used here, it is well to observe 
that during all the early part of their recognized exist- 
ence the bacteria were regarded as animal organisms and 
classed among the infusoria. Tyndall, stimulated by the 
work of Pasteur, conclusively proved that the micro-or- 
ganismal germs were in the dust suspended in the atmos- 
phere, not ubiquitous in their distribution. 
His experiments were very ingenious and are of much 
interest. First preparing light wooden chambers, with 
one large glass window in the front and one smaller win- 
dow in each side, he arranged a series of test-tubes in the 
bottom, half in and half out of the chamber, and a pipette 
in the top, working through a rubber diaphragm, so that 
when desired,the tubes, one by one could be filled through 
it. The chamber was first allowed to stand until all the 
contained dust had settled, and was then submitted to an 
